Quadrants, Regions, and Numbering

The Foundation of Dental Radiography

🎯 Learning Objectives

  • Divide the oral cavity into 4 Quadrants and 2 Arches.
  • Identify the Anterior and Posterior regions of the mouth.
  • Master the Universal Numbering System (1-32).
  • Understand the difference between Primary (A-T) and Permanent dentition numbering.

1. Dividing the Mouth

In radiography, we divide the mouth into sections to ensure we capture every tooth. You must know these divisions for mounting purposes:

Arches

Maxillary: The upper arch (part of the skull).
Mandibular: The lower arch (the movable jaw).

Quadrants

The mouth is divided into 4 quarters: Upper Right, Upper Left, Lower Left, and Lower Right.

2. Anterior vs. Posterior

This distinction is critical for choosing the correct sensor size and Rinn holder color.

  • Anterior: The “front” teeth. Includes Incisors and Canines (Cuspids). (Rinn Color: BLUE)
  • Posterior: The “back” teeth. Includes Premolars (Bicuspids) and Molars. (Rinn Color: YELLOW)

3. Universal Numbering System

The DANB RHS exam uses the Universal Numbering System. You must be able to identify a tooth by its number instantly.

Dentition Type Numbering Method
Permanent (Adult) Numbered 1 through 32. Starts at the Upper Right 3rd Molar (#1) and ends at the Lower Right 3rd Molar (#32).
Primary (Child) Lettered A through T. Following the same clockwise path as adult teeth.

🎓 DANB EXAM FOCUS: The Midline

In the Universal System, tooth numbers 8 & 9 (Maxillary) and 24 & 25 (Mandibular) meet at the Midline. If an exam question shows a PA of the midline, you are looking at the Centrals!

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